Fotossíntese, concentração de nutrientes e produtividade do feijoeiro submetido à aplicação de subdoses de glyphosate
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Data
2019-03-29
Autores
Bortolheiro, Fernanda Pacheco de Almeida Prado [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Glyphosate em subdoses pode estimular o crescimento das plantas. O efeito estimulatório de baixas doses de um composto tóxico é conhecido como hormese. Estudos como este são de fundamental importância para a adoção do manejo desta tecnologia. A hipótese desta pesquisa foi que subdoses de glyphosate promovem alterações a nível morfológico, fisiológico, nutricional e de produção em plantas de feijoeiro comum. Deste modo, o objetivo foi avaliar as alterações morfológicas, nutricionais, fisiológicas e na produtividade de grãos do feijoeiro comum de ciclo precoce submetido à aplicação de subdoses de glyphosate e se esses efeitos são influenciados pelas épocas de semeadura da cultura. Os experimentos foram conduzidos em campo e a cultivar utilizada foi a IAC Imperador, feijoeiro comum de ciclo precoce. O delineamento experimental adotado foi de blocos ao acaso, constituído de doses de glyphosate aplicadas no estádio fenológico V4, com quatro repetições. Foram realizados dois experimentos, o primeiro na safra de inverno e o segundo na safra das águas, no ano de 2016. Na safra de inverno, os tratamentos consistiram em cinco subdoses de glyphosate (0; 1,8; 7,2; 12 e 36 g de equivalente ácido (e.a.) ha-1), na safra das águas, os tratamentos consistiram em sete subdoses de glyphosate (0; 1,8; 7,2; 12; 36; 54 e 108 g de e.a. ha-1). Foram avaliados: altura de plantas, área foliar, massa de matéria seca de folhas, caule e parte aérea, taxa de crescimento da cultura (TCC), taxa de crescimento relativo (TCR), taxa de assimilação líquida (TAL), razão de área foliar (RAF), área foliar específica (AFE) e peso específico de folha (PE), teores de macro e micronutrientes nas folhas e grãos, conteúdo de clorofila a, b, total e carotenoides, taxa de assimilação de CO2, condutância estomática, taxa de transpiração, concentração interna de CO2, eficiência instantânea de carboxilação da rubisco, número de vagens por plantas, número de grãos por planta, número de grãos por vagem, massa de 1000 grãos e produtividade de grãos. A aplicação de subdoses de glyphosate proporcionou alterações, com influência da época de cultivo, nas variáveis avaliadas para o feijoeiro comum. Não foi observada uma dose única que beneficiasse todas as variáveis avaliadas em folhas e grãos do feijoeiro, no entanto, na safra de inverno podem ser destacas as doses, 36 g e.a. ha-1 por promover o crescimento das plantas; as doses 1,8; 7,2 e 36 g e.a. ha-1 por aumentar o teor de nutrientes e a dose 7,2 g e.a. ha-1 por incrementar a produtividade de grãos. Na safra das águas, a dose 36 g e.a. ha-1 promoveu o crescimento das plantas, a dose 12 g e.a. ha-1 incrementou o teor de nutrientes e a dose 36 g e.a. ha-1 aumentou a produtividade de grãos.
Glyphosate low doses can stimulate plant growth. The stimulatory effect of low dose use of a toxic compound is known as hormesis. Studies like this are of fundamental importance for the adoption of this technology. The hypothesis of this research is that glyphosate subdoses promote changes at the morphological, physiological, nutritional and production levels in common bean plants. Thus, the objective of this work was to evaluate if the application of glyphosate low doses promotes changes in common bean growth, physiology, nutritional and productivity and whether these effects are influenced by the planting seasons. Two experiments were conducted in the field and the cultivar used was the IAC Imperador, common bean of early cycle. The experimental design was a randomized block design, consisting of doses of glyphosate and one season of application (phenological stage V4), with four replications. Two experiments were carried out in 2016, the first in the winter season and the second in the water season. In the winter season, treatments consisted of five glyphosate sub-doses (0, 1.8, 7.2, 12 and 36 g of acid equivalent (a.e.) ha-1), in the water season, treatments consisted of seven subdoses of glyphosate (0.8, 7.2, 12, 36, 54 and 108 g of a.e. ha-1). Plant height, leaf area, leaf dry mass, stem dry mass, shoots dry mass, growth rate (GR), relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA), specific leaf weight (SLW), nutrient content on leaves and grains, chorophyll a, b, total and carotenoids content, CO2 assimilation rate, stomatal conductance, transpiration rate, CO2 internal concentration, instantaneous carboxylation efficiency of rubisco, number of pods per plant, number of grains per plant, number of grain per pod, mass of 1000 grains and grain yield were evaluated. The application of glyphosate low doses, influenced by the growing season, resulted in changes in the evaluated parameters in common bean. There was no single dose that benefited all the variables evaluated in leaves and grains of common beans, however, in the winter season, the dose 36 g a.e. ha-1 promoted plant growth, the doses 1.8; 7.2 and 36 g a.e. ha-1 increased nutrient content and the dose 7.2 g a.e. ha-1 increased grain yield. In the water season, the dose 36 g a.e. ha-1 promoted plant growth, the dose 12 g a.e. ha-1 increased nutrient content and the dose 36 g a.e. ha-1 increased grain yield.
Glyphosate low doses can stimulate plant growth. The stimulatory effect of low dose use of a toxic compound is known as hormesis. Studies like this are of fundamental importance for the adoption of this technology. The hypothesis of this research is that glyphosate subdoses promote changes at the morphological, physiological, nutritional and production levels in common bean plants. Thus, the objective of this work was to evaluate if the application of glyphosate low doses promotes changes in common bean growth, physiology, nutritional and productivity and whether these effects are influenced by the planting seasons. Two experiments were conducted in the field and the cultivar used was the IAC Imperador, common bean of early cycle. The experimental design was a randomized block design, consisting of doses of glyphosate and one season of application (phenological stage V4), with four replications. Two experiments were carried out in 2016, the first in the winter season and the second in the water season. In the winter season, treatments consisted of five glyphosate sub-doses (0, 1.8, 7.2, 12 and 36 g of acid equivalent (a.e.) ha-1), in the water season, treatments consisted of seven subdoses of glyphosate (0.8, 7.2, 12, 36, 54 and 108 g of a.e. ha-1). Plant height, leaf area, leaf dry mass, stem dry mass, shoots dry mass, growth rate (GR), relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA), specific leaf weight (SLW), nutrient content on leaves and grains, chorophyll a, b, total and carotenoids content, CO2 assimilation rate, stomatal conductance, transpiration rate, CO2 internal concentration, instantaneous carboxylation efficiency of rubisco, number of pods per plant, number of grains per plant, number of grain per pod, mass of 1000 grains and grain yield were evaluated. The application of glyphosate low doses, influenced by the growing season, resulted in changes in the evaluated parameters in common bean. There was no single dose that benefited all the variables evaluated in leaves and grains of common beans, however, in the winter season, the dose 36 g a.e. ha-1 promoted plant growth, the doses 1.8; 7.2 and 36 g a.e. ha-1 increased nutrient content and the dose 7.2 g a.e. ha-1 increased grain yield. In the water season, the dose 36 g a.e. ha-1 promoted plant growth, the dose 12 g a.e. ha-1 increased nutrient content and the dose 36 g a.e. ha-1 increased grain yield.
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Palavras-chave
Phaseolus vulgaris L., Hormese, Análise quantitativa de crescimento, Nutrição mineral, Trocas gasosas, Produtividade de grãos, Hormesis, Quantitative growth analysis, Mineral nutrition, Gas exchange, Grain yield